In an exhaust gas purification apparatus in an internal combustion engine, a plurality of catalysts may sometimes be arranged in series to one another in an exhaust passage of the internal combustion engine and it arrange. For example, a first patent document describes a technique in which an oxidation catalyst, an HC adsorbent and an NOx purification catalyst are arranged in series in an exhaust passage of an internal combustion engine in this order from an upstream side thereof. An oxidation catalyst in this first patent document has a through hole of a large diameter formed therein. This through hole forms a bypass passage through which HC contained in an exhaust gas passes.
In addition, a second patent document describes a technique in which a reforming catalyst that reforms the fuel injected from a fuel injection means is arranged at an upstream side from an NOx storage reduction catalyst disposed in an exhaust passage. The reforming catalyst in this second patent document is disposed in the central portion of the exhaust passage, whereby a bypass passage through which an exhaust gas flows is formed on an outer periphery of the reforming catalyst.
Moreover, a third patent document discloses a construction in which a three way catalyst and a catalyst having an HC adsorption function and an HC oxidation function are arranged in an exhaust passage of an internal combustion engine in this order from an upstream side thereof.
Further, a fourth patent document discloses a construction in which two catalysts each having an HC adsorption function and an HC oxidation function are arranged in series in an exhaust passage of an internal combustion engine. In this fourth patent document, there is described a technique that controls an air fuel ratio in accordance with the state of each catalyst so as to suppress the deterioration of exhaust emission.
[First Patent Document]
Japanese patent application laid-open No. 2002-242665
[Second Patent Document]
Japanese patent application laid-open No. 2005-127257
[Third Patent Document]
Japanese patent No. 3470597
[Fourth Patent Document]
Japanese patent application laid-open No. 2000-2133